1. Field of the Invention
The present invention relates to a base board for a printed circuit board panel which permits easy inspection of a printed circuit by means of a fluorescence-applied circuit pattern inspection machine used for the inspection of printed circuit patterns and which is not altered in the properties as a printed circuit board.
2. Prior Art of the Invention
The circuit pattern of a printed circuit board is conventionally inspected by a direct continuity method using a probe, a metallurgical microscope-applied method using reflected light from a metal conductor circuit pattern, or a method using a soft X-ray.
The circuit pattern is recently beginning to be inspected by a more accurate and highly efficient method in which a pattern of fluorescence generated from the circuit pattern of a manufactured printed circuit board is compared with a pattern of fluorescence generated from the circuit pattern of a reference normal circuit pattern by means of a phenomenon that the resin layer of a printed circuit board generates fluorescence under irradiation with excited light while a conductor pattern does not generate fluorescence.
When, however, there is an internal layer of a circuit or when the resin layer is too thin, there are some cases where insufficient inspection is possible, since fluorescence is not sufficiently strong, or the fluorescent pattern is affected by the presence or absence of the conductor circuit of the internal layer, the presence or absence of the conductor circuit on the surface opposite to the surface to be inspected, or a difference caused by whether or not a pigment and a filler are used.
To overcome the above defect, JP-A-3-2258 discloses a method using a fluorescent brightener, specifically a coumarin-containing fluorescent brightener. In this method, however, the amount of fluorescence is sometimes insufficient or the amount of fluorescence having a wavelength with which to inspect a pattern is sometimes small. The defect with this method is that when the amount of the fluorescent brightener is increased to overcome the above problem, the properties of the base board alter.